Phosphorus

Phosphorus is a nonmetallic chemical element that is a member of Group VA in the periodic table. The chemical symbol for phosphorus is P, its atomic number is 15, and its atomic weight is 30.975. Phosphorus was first prepared by German alchemist Hennig Brandt in 1669, in the course of his search for the philosopher's stone he obtained from a residue of evaporated urine a white solid that glowed in the dark and ignited spontaneously in air. The name phosporus (from the Greek for "light bringing"), which at that time was used for any substance that glows of itself, was eventually appropriated to this element. Phosphorus does not occur in elemental form in nature; it is found most commonly in apatite minerals such as fluorapatite.

Allotropes of Phosphorus
About ten forms of the element are known. White phosphorus consists of molecular P4 and is waxlike substance, very toxic and extremely flammable. When it is exposed to air in the dark, it emits a greenish light and gives off white fumes. It can ignite spontaneously. White phosphorus is used in incendiary and napalm bombs and in rat poison.

Red phosphorus, a more stable form than white, can be obtained by heating white phosphorus to 250^oC in a closed vessel. Red phosphorus is often considered a mixture of white and black phosphorus. It nether phosphoresces nor spontaneously burns in air. It is used in industry as part of the coating industry of safety matches and in the manufacture of tracer bullets, smoke screens, and sky writing compound.

When heated to temperature near 300^oC for several days, red phosphorus is converted to black phosphorus. Black phosphorus is flaky, like graphite, and has some metallic properties. It is the least reactive of the forms.

Phosphates
Nearly all the phosphorus used in commerce is in the form of phosphates, the salt derived from phosphoric acid, H₃PO₄. Large amounts of phosphate containing fertilizer are used to enhance soil fertility. Sodium triphosphate, Na₅P₃O₁₀ is used in detergents because, it softens water and disperses inorganic soiling substances. A serious disadvantage of using phosphates later end up in natural bodies of water, where to proliferate. Phosphates are also used in toothpases, Ca(H₂PO₄)₂, and sodium acid pyrophosphate, Na₂H₂P₂O₇, are leavening agents used in taking powder.

Biological Role of Phosphorus
Phosphorus, exclusively in the form of phosphates, is found in all forms of the Phosphates are essential to the energy transfer reactions necessary to sustain life processes, to a number of coenzymes, and to nucleic acids.

Phosphates are also important ingredients of bone, the human skeleton contains about 1.4 kg (about 3 lb) of phosphates as calcium phosphates, Ca₃(PO₄)₂. A phosphorus deficiency causes fatigue, weakness, and a decreased attention span. A severe deficiency may lead to seizures, coma or even death.

Arsenic Substance

Arsenic is a metallic chemical element in Group VA of the periodic table. Its symbol is As, its atomic number is 33, and its atomic weight is 74.9216. The Earth's crust contains only about 5.5 parts arsenic per million, but it occurs in many minerals.

Arsenic exist in three allotropic modifications, the yellow (alpha) and the black (betha) and metallic, or gray (gamma). Normally arsenic is found in its metallic form, which is the most stable and its normal pressure does not melt but sublimes at about 615^oC. It forms alloy with other metalls. The alpha and betha modifications have no metallic properties. Arsenic is fairly reactive. Above 400^oC it burns with a bluish flame, forming arsenic trioxide, As2O3. This compound is know as white arsenic and is used as a rat poison.

The toxic quality of arsenic has been known since ancient times. In the human body it accumulates in the nails and the hair, where it can be detected, even in the bodies of persons long dead, by the atomic absorption method. The acute symptoms are diarrhea and cramps. In cases of chronic poisoning, anemia and paralysis may appear. If there is prolonged contact with the skin, malignant skin tumors can develop. In medicine, 4-aminobenzene arsenic and 4-hydroxybenzene arsenic compounds are used to treat certain infections. The best known is Salvarsan, an antisyphilis drug. Commercially, arsenic is added to lead to harden it and is used in the production of herbicides and pesticides.

Portable PH Meter

For field engineer that usually measure a pH of the liquid on the environment that they are founded, they usually use portable pH meter in order can easily to check the pH condition of the liquid flow.

The Model Personal pH/ORP Meter is a highly accurate, portable pH meter for
laboratory and field application. With its self-diagnostic function, the PH meter provides
precise measurement of pH and ORP (oxidation-reduction potential). Measurement
results can be stored and stored data can be checked on the meter display any time. The
PHmeter is of waterproof construction so that it can safely be used outdoors on a rainy day, and can also withstand being accidentally dropped into water.
Some Feature should be own by pH meter equipment:

• Water resistant case
• Simple calibration
• Automatic calibration based on preprogrammed data of standard solutions or manual calibration can be done through simple key operations.
• Calendar and clock function
• Internal clock functions allow “one-touch checking” of measurement date and time.
• Data storage function
• Up to 300 measured pH values along with their respective solution temperatures, dates and times, can be stored and stored data can be checked on the display any time.
• Auto power off function
• The meter will turn off power automatically if not operated during a preset time period.
• The auto power off time can be user configurable in the range of 1 to 120 minutes in increments of 1 minute. The auto power off function can be disabled, where the meter should be used with care to conserve the batteries.
• Alarm clock function
• The meter can issue an alarm signal at a specified time. Even when meter power is turned off, the internal clock can issue an alarm signal.
• Self-diagnostic function
• A relevant error message will appear based on the self-diagnostic function.
• Large, clear LCD
• A measured pH (mV) value, solution temperature, date and time are clearly viewed on the display.
• Compact, lightweight, and handy
• The meter fits comfortably your hand and also stands firm on the table.

For portable pH meter it should cover the following specification.

Measuring range: pH: 0 to 14 pH
ORP: -2000 to 2000 mV
Temperature: 0 to 100^oC
Resolution: pH: 0.01 pH
ORP: 0.1 mV (-199.9 to 199.9 mV)
1 mV (-2000 to -200 mV and 200 to 2000 mV)
Temperature: 0.1^oC
Repeatability (without sensor):
pH: ± 0.01 pH 61 digit
ORP: ± 1 mV 61 digit
Accuracy (Temperature): ± 0.7^oC (0 to 70^oC)
                                       ±1^oC (above 70^oC)
Temperature compensation (glass electrode emf — temperature characteristics):
Automatic compensation (or manual compensation*1)
Solution temperature: 0 to 80^oC (or 0 to 100^oC*1) (0 to 50^oC when a KCl replenish free type sensor and its sensor cable are immersed in water)

Solution conductivity: 50 μS/cm or more
Ambient temperature: 0 to 50^oC
Construction: Protection class IP67 (IEC 60529)
Power source: 2x AA batteries (LR6)
Auto power off function (time configurable: 1 to 120 minutes)
Battery life: Approximately 600 hours*2 of continuous use (battery type and operating condition dependent)
Dimensions: Approximately 150(H) x 61(W) x 42(D) mm (not including connector part)
Weight: Approximately 220 g (including batteries)
*1: When a needle type or test tube size pH sensor is used.
*2: When alkaline batteries are used.

Characteristic of Hydrogen

Numerical characteristic of hydrogen are summarized on the below table. The values on the latter table are for the ordinary isotropic mizture of hydrogen containing about one part of deuterium in 5000 and the ordinary ortho para mixture.

Numerical Constant of Hydrogen

Property	Numerical Value
Critical Temperature, oK	32
Critical pressure, atm	20
Density of gas, gram/liter at 0 oC, 1 atm	0
Density of liquid, gram/ml	0.071
Solubility in H2O, ml/100 grams as 25 oC	1.5

Chemically, hydrogen combines with most, of the non metallic elements and with many of the metals to produce compounds called hydrides. Hydrogen serves as a reducing agent toward many metal oxides oxides and toward double and triple bounds involving carbon. Characteristic reactions of hydrogen, in general reaction are indicative of the tendency of hydrogen to bonds with highly electropositive elements are completely ionic those with higly electromagnetive posses appreciable partial ionic character.

Bond Chemical Types

The important linkages which hold together the components of crystalline solids and their general characteristics may be summarized as follows:

1. Ionic Linkages or ionic bond
In which the crystals are made up of regular geometrical arrangements of positive and negative ions. Such solids tend to possess high melting and boiling points, are hard and difficult to deform, and tend to be soluble in polar solvents. When dissolved in such solvents as fused, they are excellent conductors. Crystals characterized by such linkages are called ionic crystals. The salts are examples.

2. Covalent Linkages
In which the crystals are made up of molecules produced by the sharing of electrons, usually to pairs, between atoms of the elements involved. Such solids posses properties essentially opposite from those outlined for ionic crystals, although the partial ionic characters of many covalent bonds effect corresponding modifications. The following types of covalent crystalline solids may be distinguished.

• Non Polar molecular crystals, where weak attractive forces resulting from electronic motions are responsible for crystal stability. Such crystals are soft and easily melted or vaporized. Solid hydrogen, solid helium, and solid carbon tetrachloride are examples.
• Polar molecular crystals, where orientation of dipoles result in somewhat greater attractive forces and consequent increases in crystal stability. Although such materials are non-conductors, they do have enhanced melting points, boiling points, and solubilities in polar solvents over strictly non-polar crystals. Solid water, hydrogen chloride, etc. are examples.
• Atomic crystals, where three dimensional covalent bonding results in giant molecules. Such crystals are resistant to deformation and are often harder and higher melting than ionic crystals. Diamond, silicon carbide, etc. are examples.

3. Metallic Linkages
In which mobile electrons provide the necessary forces for crystal stability. Such solids are characterized by toughness, malleability, ductility, high conductivity, luster, and insolubility in liquids other than molten metals. Any metal would be an example.